Iran war rattles stocks: how past market reactions could affect your portfolio

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The recent flare-up in the Middle East sent U.S. stocks tumbling Tuesday as investors weighed the risk to trade routes and energy supplies — a familiar pattern after sudden geopolitical shocks that often produces a short-lived market reaction. What happens next matters for portfolios and fuel prices, and historical data offers guarded perspective for worried investors.

Stocks recovered some ground Wednesday, but the sell-off Tuesday left major indexes lower. The S&P 500 closed the day down roughly 0.9%, the Dow Jones Industrial Average fell about 0.8%, and the tech-heavy Nasdaq Composite lost just over 1%. Earlier in the session, each index had dropped more than 2.5% before buyers stepped in.

Traders pointed to concerns about disruptions to shipping — especially through the Strait of Hormuz, a choke point for international oil shipments — until President Donald Trump said the U.S. would help ensure commercial vessels can transit the waterway. Energy markets initially spiked after news of military action in the region, then eased from the worst levels.

What history says about market shocks

Past conflicts show the market often reacts quickly and then stabilizes. An analysis by the Stock Trader’s Almanac of 17 geopolitical shock events since 1939 finds the average one-week decline in the S&P after such a shock is about 1.09% — a pullback, not a permanent shift.

Most common short-run move: A modest one-week drop in the S&P, averaging roughly 1%.

Extreme examples: The biggest one-week gain in the dataset was 13.5% after Germany invaded Poland in 1939; the largest one-week loss was 17.9% when Germany invaded France in 1940.

One-year range: Twelve months after a new crisis the S&P has averaged a gain of about 2.9%, though outcomes vary widely — from a 32% one-year jump after the Gaza War began in October 2023 to a 34% loss following the 1973 Arab oil embargo.

Recent episodes also illustrate mixed short- and medium-term results. After Russia’s invasion of Ukraine in February 2022, the S&P gained 3.3% in the first week but was down about 6% after a year — a performance shaped by rising inflation and a weaker economic backdrop, according to Jeffrey Hirsch, editor in chief of the Stock Trader’s Almanac.

“This time around, the economy appears to be on firmer ground,” Hirsch said, while noting it is still early in the current conflict and that sustained pressure on oil would likely push prices higher.

Volatility readings and market signals

The CBOE Volatility Index — commonly called the VIX, which tracks expected S&P volatility over the next 30 days — sat around 23 on Tuesday. That is well below spikes seen in some previous stress events; for comparison, the VIX rose above 50 during the market rout tied to tariff uncertainty in April 2025.

Higher VIX readings typically signal greater short-term fear among investors, but they do not predict long-term direction. Where prices go from here will depend on how widely the conflict spreads, whether shipping is disrupted for an extended period, and how central banks and governments respond.

Practical takeaways for investors

For most long-term investors, financial advisers generally urge patience rather than panic. History shows that sitting out volatile periods can carry real costs: research from Hartford Funds demonstrates that missing the market’s best days over long stretches materially reduces returns.

Missing the 10 best trading days in a 30-year span through 2024 would have cut returns by roughly half.

Missing the 30 best days over the same period would have slashed returns by about 83%.

Many of the market’s best days occur during or immediately after bear markets, underscoring the risk of exiting at the wrong time.

Still, volatility can reveal a mismatch between an investor’s stated goals and their emotional comfort with risk. Advisors say small portfolio adjustments — shifting a few percentage points from equities into bonds, for example — may be appropriate for those who find the swings unmanageable.

“It usually involves modest tweaks,” said advisor Baker, describing moves such as dialing equity exposure down from 80% to 70% or 60% while increasing bonds. “If it helps you sleep at night, trimming some risk can be reasonable.”

Key questions going forward

The path of markets will hinge on several concrete developments:

Whether hostilities expand beyond current actors;

How long shipping through the Strait of Hormuz remains at risk;

Near-term movement in oil prices and the resulting impact on inflation and growth expectations.

Investors watching for clues should monitor energy markets, volatility gauges, and official statements about efforts to keep trade routes open. Short-term turbulence may be expected, but historical data suggests it is not necessarily the start of a prolonged market collapse.

For those unsure about their allocation, a review of the investment timeline and risk tolerance — and, if needed, consultation with a trusted financial professional — remains the most prudent course.